Google build genuinely useful products, and use the knowledge it gains about you to show (generally somewhat useful) ads, and generally stays out of your way.
Facebook on the other hand desperately tries to manipulate you into consuming as much time as possible on their platform at almost any cost, using lowest common denominator tricks.
Try blocking all Google domains via a hosts file, and you'll see that they have put their hooks into all kinds of systems, and do so in ways that seriously impede how normal web-pages should function.
HN has noprocrast because YC has a financial interest in their founders not wasting their time, or becoming addicts. Can you imagine FB implementing noprocrast? It goes against everything they do.
* https://twitter.com/zeynep/status/973716995521748992
* https://twitter.com/Limerick1914/status/972837152940855296
This doesn't mean YouTube staff are purposefully designing the algorithm to specifically trend towards extremism: this can fall out naturally from human psychology and ML algorithms that note which videos increase engagement and recommend videos based on user interest and recommending videos that will increase the user's time on site.
I think this is worth looking into in a more methodical manner. You can dismiss it as cherry-picking, but I think it's something reasonable people can be concerned about. And these services and products should be looked at separately, determining which parts are good and which parts are bad.
Probably nothing. If you don't have something constructive to add, don't.
As much as I feel obligated to engage with others constructively, I feel obliged to discourage and make others aware of nonconstructive behavior. I take your point that this thread is going nowhere, though, and I will stop. I acknowledge I may have gone too far.